運用CFD數值方法於SDI引擎層狀進氣之研究

An Investigation on Stratified Charging for SDI Engine by CFD Numerical Method

楊清潭(Ching-Tan Yang)

指導教授 ： 吳浴沂

國立臺北科技大學/機電學院/車輛工程系所/碩士(2011年)

https://doi.org/10.6841/NTUT.2011.00719

摘要

本研究藉由計算流體力學商用軟體進行缸內流場分析探討層狀進氣對SDI(semi-direct injection)引擎的影響，歸納出提升SDI引擎效率之方針。其中SDI引擎包含有渦流產生器及半直接噴射(SDI)系統之技術。為得知SDI引擎之特性，首先進行汽缸頭流量試驗，了解原廠進氣道及渦流產生器之流量係數及渦旋比。接著進行引擎實驗，測試原引擎及SDI引擎之稀薄燃燒極限。之後運用CFD軟體ANSYS CFD/FLUENT建立引擎數值模型，模擬流量試驗情形並計算出模擬結果與流量試驗結果作驗證。最後則將驗證過的引擎數值模型進行暫態流場計算分析，探討SDI引擎缸內流場的流動現象。
實驗結果顯示，原廠進氣道及渦流產生器的流量係數與渦旋比分別為0.493與0，及0.158與1.67。稀薄燃燒測試結果顯示，原引擎及SDI引擎之稀薄燃燒極限分別為空氣過剩比(excess air ratio, λ) 1.1及λ=1.5。模擬結果顯示，原廠進氣道之流量係數試驗值與CFD模擬值的相對誤差為1.9%而渦旋比之CFD模擬值為0.09。渦流產生器之流量係數及渦旋比試驗值與CFD模擬值的相對誤差分別為3.0%及3.2%。最後綜合模擬結果與實驗結果得知，進氣渦流確實可增強缸內紊流，提升燃燒效率，因此SDI引擎可獲得較佳的油耗及稀薄燃燒極限，故SDI引擎效率與缸內紊流強度有關。

關鍵字

計算流體力學 ； 渦流 ； 稀薄燃燒 ； 數值模型

並列摘要

In this study, stratified charging affects effect of semi-direct injection (SDI) engine is investigated by calculate in-cylinder flow field with computational fluid dynamics (CFD) commercial software. It induces the courses of increasing efficiency of SDI engine. The SDI engine includes the technologies of swirl generator and SDI system. In order to know the characteristics of SDI engine, this study does the flow test first. By doing this test, we could get the data of flow coefficient and swirl ratio of original port and swirl generator. Follow by the engine experiment of original engine and SDI engine, so that we know the lean burn limit of both engines. Finally, the engine numerical model is established by ANSYS CFD/FLUENT, the CFD software. It will simulate the situation of flow test which verify the results of flow test. Furthermore, the transient flow is calculated by verified engine numerical model. And this study uses the simulation results to investigate the phenomena of in-cylinder flow of SDI engine.
Experiment results of flow coefficient and swirl ratio of original port are 0.493 and 0, and results of Swirl generator are 0.158 and 1.67. The lean burn test results show the excess air ratio of original engine and SDI engine are 1.1 and 1.5. Simulation results show the error percent of flow coefficient for original port is 1.9%; swirl ratio of original port is 0.09. Error percent of flow coefficient and swirl ratio for swirl generator are 3.0% and 3.2%. In conclusion, simulation results and experiment results indicate the in-cylinder turbulence can be increased by intake swirl flow, and then the combustion efficiency is also increased. For this reason, SDI engine can get better fuel consumption and lean burn limit, and the efficiency of SDI engine is reference to in-cylinder turbulence intensity.

並列關鍵字

Computational fluid dynamics ； Swirl ； Lean burn ； Numerical model

參考文獻

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